Opened 9 years ago

Closed 9 years ago

# Bug at computing a free resolution.

Reported by: Owned by: anna-lena.winz@… hannes major 3-2-0 and higher singular-kernel 3-1-6 res, sres

I get the following bug when computing the resolution of an ideal given as the kernel of a map:

```ring R_sv = 0,(x(1),x(2)),dp;
ideal ti_sv = 0;
qring r_sv = std(ti_sv);
ring R_s2v = 0,(z(1),z(2),z(3),z(4),z(5),z(6)),dp;
<^1-1*z(1)^1*z(5)^1,1*z(4)^2-1*z(1)^1*z(6)^1,1*z(5)^1*z(6)^1-1*z(3)^1*z(4)^1,1*z(5)^2-1*z(3)^1*z(6)^1;
qring r_s2v = std(ti_s2v);
ring R_sv_tensor_R_s2v = 0,(x(1),x(2),z(1),z(2),z(3),z(4),z(5),z(6)),dp;
ideal ti_sv = 0;
qring r_sv_tensor_R_s2v = std(ti_sv);
setring r_s2v;
map f = r_sv_tensor_R_s2v,1*z(2)^1,1*z(6)^1,z(1),z(2),z(3),z(4),z(5),z(6);
setring r_sv_tensor_R_s2v;
ideal sigma2 = kernel(r_s2v, f);
def L = res(sigma2,2);
```

Singular : signal 11 (v: 3160): current line:>> re=sres(std(m),i);<< Segment fault/Bus error occurred at ffff because of 10206 (r:1395233037)

Any help is much appreciated,

Best, Anna-Lena

### comment:1 Changed 9 years ago by anonymous

``` > ring R_sv = 0,(x(1),x(2)),dp;
> ideal ti_sv = 0;
> qring r_sv = std(ti_sv);
> ring R_s2v = 0,(z(1),z(2),z(3),z(4),z(5),z(6)),dp;
<^1-1*z(1)^1*z(5)^1,1*z(4)^2-1*z(1)^1*z(6)^1,1*z(5)^1*z(6)^1-1*z(3)^1*z(4)^1,1*z(5)^2-1*z(3)^1*z(6)^1;
> qring r_s2v = std(ti_s2v);
> ring R_sv_tensor_R_s2v = 0,(x(1),x(2),z(1),z(2),z(3),z(4),z(5),z(6)),dp;
> ideal ti_sv = 0;
> qring r_sv_tensor_R_s2v = std(ti_sv);
> setring r_s2v;
> map f =
r_sv_tensor_R_s2v,1*z(2)^1,1*z(6)^1,z(1),z(2),z(3),z(4),z(5),z(6);
> setring r_sv_tensor_R_s2v;
> ideal sigma2 = kernel(r_s2v, f);
> def L = res(sigma2,2);
Singular : signal 11 (v: 3160):
current line:>>          re=sres(std(m),i);<<
Segment fault/Bus error occurred at ffff because of 10206 (r:1395233037)
trying to restart...
```

### comment:2 Changed 9 years ago by Oleksandr

Component: dontKnow → singular-kernel modified (diff) res sres added changed from somebody to hannes dontKnow → major

### comment:3 Changed 9 years ago by Oleksandr

Description: modified (diff)

### comment:4 Changed 9 years ago by Oleksandr

Hi,

Sorry, but `ti_s2v` in `R_s2v` is missing in your code :(

could you please provide `r_sv_tensor_R_s2v` and the final `sigma2`?

### comment:5 Changed 9 years ago by anonymous

```ring R_sv = 0,(x(1),x(2)),dp;
ideal ti_sv = 0;
qring r_sv = std(ti_sv);
ring R_s2v = 0,(z(1),z(2),z(3),z(4),z(5),z(6)),dp;
ideal ti_s2v = 1*z(6)^2-1*z(1)^1*z(3)^1,1*z(4)^1*z(5)^1-1*z(1)^1*z(3)^1,1*z(4)^1*z(6)^1-1*z(1)^1*z(5)^1,1*z(4)^2-1*z(1)^1*z(6)^1,1*z(5)^1*z(6)^1-1*z(3)^1*z(4)^1,1*z(5)^2-1*z(3)^1*z(6)^1;
qring r_s2v = std(ti_s2v);
ring R_sv_tensor_R_s2v = 0,(x(1),x(2),z(1),z(2),z(3),z(4),z(5),z(6)),dp;
ideal ti_sv = 0;
qring r_sv_tensor_R_s2v = std(ti_sv);
setring r_s2v;
map f = r_sv_tensor_R_s2v,1*z(2)^1,1*z(6)^1,z(1),z(2),z(3),z(4),z(5),z(6);
setring r_sv_tensor_R_s2v;
ideal sigma2 = kernel(r_s2v, f);
def L = res(sigma2,2);
```

I am sorry, this is the full version of the code. It is generated automatically by a script, that is why some of the monomials look a little odd.

### comment:6 Changed 9 years ago by Oleksandr

looks like the problem is in the qring with zero quotient ideal:

```ring R_sv_tensor_R_s2v = 0,(x(1),x(2),z(1),z(2),z(3),z(4),z(5),z(6)),dp;
ideal sigma2 = x(2)-z(6),x(1)-z(2),z(5)^2-z(3)*z(6),z(4)*z(5)-z(6)^2,z(1)*z(5)-z(4)*z(6),z(4)^2-z(1)*z(6),z(3)*z(4)-z(5)*z(6),z(1)*z(3)-z(4)*z(5);;sigma2 = std(sigma2);
def L=sres(sigma2,2); // OK!

qring Q = std(0); // leads to the BUG!

ideal sigma2 = x(2)-z(6),x(1)-z(2),z(5)^2-z(3)*z(6),z(4)*z(5)-z(6)^2,z(1)*z(5)-z(4)*z(6),z(4)^2-z(1)*z(6),z(3)*z(4)-z(5)*z(6),z(1)*z(3)-z(4)*z(5); sigma2 = std(sigma2);
def L=sres(sigma2,2); // BUG HERE!!!
```
Last edited 9 years ago by Oleksandr (previous) (diff)

### comment:7 Changed 9 years ago by hannes

Resolution: → fixed new → closed

### comment:8 Changed 9 years ago by kroeker@…

Resolution: fixed closed → reopened

The commit does not contain a corresponding regression test.

### comment:9 Changed 9 years ago by hannes

Resolution: → invalid reopened → closed

please do not report nonsense: try "git log" and search for 587

### comment:10 Changed 9 years ago by anonymous

please do not report nonsense: try "git log" and search for 587

ok, a corresponding test was added in commit 0929ddc2c6615bd5e6fc2fcc07f26b85bdee0be9

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